IS case 503: Myelofibrotic extramedullary hematopoiesis
Imaging Sciences URMC 2010
Publication Date: 2010-09-10
Contrast enhanced coronal CT reconstruction (Fig. 1) demonstrates massive splenomegaly and multiple hypodense splenic mass lesions of varying sizes. The liver appears fatty with cirrhotic morphology, however no focal hepatic lesions are appreciated (Fig. 2). The osseous structures of the pelvis (Fig. 3) and spine (not shown) demonstrate diffuse patchy increased bone density.
Myelofibrotic extramedullary hematopoiesis
This patient had a 25-year history of myelofibrosis confirmed with bone marrow biopsy. It occurs in middle aged and elderly patients with a familial association also reported. Myelofibrosis is characterized by fibrotic replacement of the bone marrow as evidenced by increased reticulin staining and it is associated with extramedullary hematopoiesis. Increased prominence of trabecular bone often seen in the pelvis and spine leads to patchy osteosclerosis also described as a mottled appearance on radiographs or CT (Fig. 3). Patients also present with anemia, teardrop-shaped red cells (dacrocytes) on peripheral blood smear, and variable platelet and white blood cell counts. Common presenting complaints include fatigue, fever, weight loss, night sweats, as well as early satiety due to massive splenomegaly and compression on the stomach.
Splenomegaly is often a distinctive feature of myelofibrosis and is due to extramedullary hematopoiesis that can involve and diffusely enlarge almost any organ . In this patient, specimens taken after splenectomy and a liver biopsy confirmed there was myelofibrotic extramedullary hematopoiesis. On CT, splenic extramedullary hematopoiesis may appear as multiple hypodense mass lesions. These may demonstrate T1 hypointensity, T2 hyperintensity, and progressive enhancement after gadolinium administration at MRI.
Other differential considerations for splenomegaly and multiple hypodense mass lesions include lymphoma, sarcoidosis, amyloidosis, infection, and metastatic disease. Diffuse mottling of the osseous structures is a typical appearance of myelofibrosis or metastatic disease.
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